Novel 9-substituted phenyl-3,7-dimethyl-nona-2,4,6,8-tetraene esters

ABSTRACT

Novel 9-substituted phenyl-3,7-dimethyl-nona-2,4,6,8-tetraene derivatives useful as anti-tumor agents.

SUMMARY OF THE INVENTION

In accordance with this invention, it has been discovered that thecompounds of the formula: ##STR1## wherein one of R₁ and R₂ is halogenor lower alkyl and the other is halogen or lower alkoxy; R₃ and R₅ arehydrogen, halogen or lower alkyl, with the proviso that one of R₃ and R₅is other than halogen, R₄ is halogen, lower alkoxy, amino, mono(loweralkyl)amino or di(lower alkyl) amino; and R₆ is formyl, hydroxymethyl,alkoxymethyl, alkanoyloxymethyl, carboxyl, alkoxycarbonyl,alkenyloxycarbonyl, alkynyloxycarbonyl, carbamoyl, mono(loweralkyl)-carbamoyl, di(lower alkyl) carbamoyl or N-heterocyclylcarbonyl;and salts thereof are useful as anti-tumor agents.

According to the process provided by the present invention, thecompounds of formula I above and their salts are manufactured byreacting a compound of the formula: ##STR2## WITH A COMPOUND OF THEFORMULA: ##STR3## WHEREIN M IS ZERO AND N IS 1, OR M IS 1 AND N IS ZERO,ONE OF A and B is formyl and the other is either atriarylphosphoniummethyl group of the formula

    --CH.sub.2 --P[X].sub.3 .sup.+ Y.sup.-

in which X is aryl and Y is an anion of an organic or inorganic acid, ora dialkoxyphosphinylmethyl group of the formula ##STR4## Z is alkoxy; orone of A and B is halomethyl, alkylsulphonyloxymethyl orarylsulphonyloxymethyl group and the other is a sulphonylmethyl group ofthe formula ##STR5## in which E is aryl or aralkenyl which may carry oneor more electron-repelling to electron-weakly attracting substituents;R₁, R₂, R₃, R₄ and R₅ are as above; and R₇ is carboxyl, alkoxycarbonyl,alkenyloxycarbonyl, alkynyloxycarbonyl, di(lower alkyl)carbamoyl orN-heterocyclylcarbonyl; or when B is formyl, R₇ is carboxyl,alkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, di(lower alkyl)carbamoyl, N-heterocyclylcarbonyl, alkoxymethyl or alkanoyloxymethyl; orwhen B is halomethyl, alkylsulfonyloxy or arylsulfonyloxy, R₇ iscarboxyl, alkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl,di(lower alkyl) carbamoyl, N-heterocyclycarbonyl, formyl, alkoxymethylor alkanoyloxymethyl; or when B is triarylphosphoniummethyl,dialkoxyphosphinylmethyl or sulphonylmethyl; R₇ is carboxyl,alkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, di(loweralkyl)-carbamoyl, N-heterocyclylcarbonyl or formyl; and cleaving off asulphone group which may be present in the reaction product to form anadditional carbon-carbon bond, and, if desired, converting an acidobtained or an amine obtained into a salt, or converting a carboxylicacid of formula I into a carboxylic acid ester of formula I or into anamide of formula I, or converting a carboxylic acid ester of formula Iinto a carboxylic acid of formula I or into an amide of formula I, orreducing a carboxylic acid of formula I or a carboxylic acid ester offormula I to the corresponding alcohol of formula I and if desiredetherifying or esterifying said alcohol, or saponifying an alcohol esterof formula I, or oxidising an alcohol or alcohol ester of formula I tothe corresponding carboxylic acid.

DETAILED DESCRIPTION

The lower alkyl groups preferably contain from 1 to 6 carbon atoms suchas methyl, ethyl, propyl, isopropyl or 2-methylpropyl. The lower alkoxygroups likewise preferably contain from 1 to 6 carbon atoms such as themethoxy, ethoxy or isopropoxy group.

The term "halogen" includes all four halogen groups such as chlorine,fluorine, bromine and iodine. Of the halogens, fluorine and chlorine arepreferred.

The amino group can be monosubstituted or di-substituted bystraight-chain or branched-chain lower alkyl groups, e.g., by methyl,ethyl or isopropyl.

The alkoxymethyl and alkoxycarbonyl groups preferably contain alkoxygroups having 1 to 6 carbon atoms. These can be straight-chain orbranched-chain such as, for example, the methoxy, ethoxy or isopropoxygroup. However, the alkoxy groups can also be higher alkoxy groupscontaining from 7 to 20 carbon atoms, especially the cetyloxy group. Thesaid alkoxy groups can be substituted by functional groups; for example,by nitrogen-containing groups such as an optionally alkyl-substitutedamino or morpholino group, or by a piperidyl or pyridyl group.

The alkenoxycarbonyl and alkynoxycarbonyl groups also preferably containalkenoxy and alkynoxy groups containing from 2 to 6 carbon atoms suchas, for example, the allyloxy or propargyloxy group.

The alkanoyl groups present in the alkanoyloxymethyl groups arepreferably derived from lower alkanecarboxylic acids containing from 1to 6 carbon atoms (e.g. acetic acid, propionic acid or pivalic acid),but they may also be derived from higher alkanecarboxylic acidscontaining from 7 to 20 carbon atoms (e.g. palmitic acid or stearicacid).

The carbamoyl group can be monosubstituted or di-substituted bystraight-chain or branched-chain lower alkyl groups (e.g. methyl, ethylor isopropyl). Examples of such substituted carbamoyl groups are themethylcarbamoyl, dimethylcarbamoyl and diethylcarbamoyl groups.

The N-heterocyclyl portion of the N-heterocyclylcarbonyl groups ispreferably a 5-membered or 6-membered heterocyclic group which, inaddition to the nitrogen atom, may also contain an oxygen or sulphuratom or a further nitrogen atoms. Examples thereof are the piperidino,morpholino, thiomorpholino or pyrrolidino group.

Examples of compounds of formula I are:

9-(6-chloro-4-methoxy-2,3-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(2-chloro-4-methoxy-3,5,6-trimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(5-chloro-2,4-dimethoxy-6-methyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(2,6-dichloro-4-methoxy-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(2,5,6-trichloro-4-methoxy-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester;

9-(6-methyl-2,4-dimethoxy-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester; and

9-(2,4-dimethoxy-3,6-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.

The aryl groups denoted by the symbol X in the triarylphosphonium-methylgroups formulated earlier include all generally known aryl groups.However, the aryl groups are preferably mononuclear aryl groups such asphenyl or (lower alkyl)- or (lower alkoxy)-substituted phenyl groups(e.g. tolyl, xylyl, mesityl and p-methoxyphenyl). Of the inorganic acidanions denoted by the symbol Y, the chlorine, bromine or iodine ion orthe hydrosulphate ion is preferred. Of the organic acid anions, thetosyloxy ion is preferred.

The alkoxy groups denoted by the symbol Z in thedialkoxyphosphinylmethyl groups are preferably lower alkoxy groupscontaining from 1 to 6 carbon atoms, especially methoxy and ethoxygroups.

Examples of aryl or aralkenyl groups, which may carry one or moreelectron-repelling to electron-weakly attracting substituents on thearyl moiety and which is denoted by the symbol E in the sulphonylmethylgroups, are phenyl and styryl, both of which may be substituted in theo-, m- and/or p-position by

methoxy, phenoxy, acetoxy;

dimethylamino, phenylmethylamino, acetylamino;

thiomethyl, thiophenyl, thioacetyl;

chloro, bromo;

cyano; or

nitro in the m-position.

Among the preferred compounds of formula II are compounds of theformula: ##STR6## wherein m is zero or 1; one of the R₁ and R₂ ishalogen or lower alkyl and the other is halogen or lower alkoxy; one ofR₃ and R₅ are hydrogen, halogen or lower alkyl; with the proviso thatone of R₃ and R₅ is other than halogen; R₄ is halogen, lower alkoxy,amino, mono(lower alkyl) amino, or di(lower alkyl)amino; X is aryl and Yis an anion of an organic or inorganic acid; and a compound of theformula: ##STR7## wherein m is zero or 1; R₁ and R₂ is halogen or loweralkyl and the other is halogen or lower alkoxy; R₃ and R₅ are hydrogen,halogen or lower alkyl with the proviso that one of R₃ and R₅ is otherthan halogen, R₄ is halogen, lower alkoxy, amino, mono(lower alkyl)aminoor di(lower alkyl) amino; and Z is alkoxy; and

a compound of the formula: ##STR8## wherein m is zero or 1; one of R₁and R₂ is halogen or lower alkyl; and the other is halogen or loweralkoxy; R₃ and R₅ are hydrogen, halogen or lower alkyl; with the provisothat one of R₃ and R₅ is other than halogen; R₄ is halogen, loweralkoxy, amino, mono(lower alkyl) amino or di(lower alkyl)amino and E isaryl or aralkenyl; said aryl or aralkenyl may be unsubstituted orsubstituted with one or more electron-repelling to electron-weaklyattracting substituents on the aryl moiety.

The starting materials of formula II, are, in part, novel and such novelstarting materials also form part of this invention. They can beprepared, for example, in the following manner:

Compounds of formula II in which m is zero and A is triphenylphosphoniummethyl group [II-a] or a dialkoxyphosphinylmethyl group [IIc] can beprepared, for example, by treating a corresponding (R₁ -R₅)-benzene withformaldehyde in the presence of a hydrohalic acid (e.g. in the presenceof concentrated hydrochloric acid optionally in a solvent, especially ina glacial acetic acid) and reacting the resulting (R₁ - R₅)-benzylhalide [a halide of formula II in which the m is zero and A ishalomethyl (IIi)] in a manner known per se with a triarylphosphine in asolvent, preferably with triphenylphosphine in toluene or benzene, orwith trialkylphosphite, especially with triethylphosphite.

An alkoxy group can be introduced into the aforementioned (R₁-R₅)-benzene by, for example, alkylation of a hydroxy group alreadypresent. For example, the corresponding phenol, preferably in a solvent(e.g. an alkanol) and in the presence of a base (e.g. potassiumcarbonate) can be reacted with an alkyl halide (e.g. methyl iodide) ordimethylsulphate.

Compounds of the formula II in which m is 1 and A is triarylphosphoniummethyl group [IIb] or a dialkoxyphosphinylmethyl group (IId) can beprepared, for example, in the following manner: A corresponding (R₁ -R₅)-benzene is first subjected to formulation; for example, by allowinga formylating agent to act on said (R₁ -R₅)-benzene. This can be carriedout, for example, by carrying out the formylation in the presence of aLewis acid. As formulating agents, there may be mentioned, inparticular, orthoformic acid esters, formyl chloride anddimethylformamide. Especially suitable Lewis acids are the halides ofzinc, aluminium, titanium, tin and iron, such as zinc chloride, aluminumtrichloride, titanium tetrachloride, tin tetrachloride and iontrichloride, as well as the halides of inorganic and organic acids suchas, for example, phosphorus oxychloride and methanesulfphonyl chloride.

If the formylating agent is present in excess, the formylation may becarried out without the addition of a further solvent. However, it isgenerally recommended to carry out the formylation in an inert solvent(e.g. nitrobenzene or a chlorinated hydrocarbon such as methylenechloride). The formylation can be carried out at temperature between 0°C. and the boiling point of the formylation mixture.

The (R₁ -R₅)-benzaldehyde obtained can be subsequently converted in amanner known per se by condensation with acetone in the cold (i.e., at atemperature of about 0° C. - 30° C.) in the presence of alkali (e.g.dilute aqueous sodium hydroxide) into a (R₁ - R₅)-phenyl-but-3-en-2-onewhich can be converted into a corresponding (R₁ -R₅)-phenyl-3-methyl-3-hydroxy-penta-4-en-1-yne in a manner known per seby means of an organo-metallic reaction (e.g. a Grignard reaction withthe addition of acetylene). The resulting tertiary acetylenic carbinolis subsequently partially hydrogenated in a manner known per se using apartly deactivated noble metal catalyst (Lindlar catalyst). Theresulting tertiary ethylenic carbinol can be subsequently be convertedinto the desired phosphonium salt of formula IIb in which the symbol mstands for 1 under allylic rearrangement by treatment with atriarylphosphine, especially triphenylphosphine, in the presence of amineral acid (e.g. a hydrogen halide such as hydrogen chloride orhydrogen bromide or sulphuric acid) in a solvent (e.g. benzene). Thetertiary ethylenic carbinol can also be halogenated to give a halide ofthe formula II in which m is 1 and A is halomethyl group (IIk) and thehalide can be converted with a trialkylphosphite (e.g.triethylphosphite) into a corresponding phosphonate of the formula IId.

Compounds of formula II in which the symbol m is zero and A issulphonylmethyl [IIe] can be prepared, for example, by dissolving a (R₁-R₅)-phenyl or a corresponding halobenzene in a polar solvent (e.g. analkanol such as methanol, ethanol or isopropanol, tetrahydrofuran,dimethylformamide or glacial acetic acid) and treating the solution atroom temperature with a sulphinic acid of the formula: ##STR9## in whichthe symbol E has the significance given earlier, or with an alkali saltof said sulphinic acid. The sulphone can be isolated from the reactionmixture by, for example, making the reaction mixture neutral by theaddition of an aqueous sodium bicarbonate solution and extracting thesulphone with an organic solvent (e.g. ethyl acetate or ether).

Compounds of formula II in which m is 1 and A is sulphonylmethyl [IIf]can be prepared in an analogous manner by reacting a (R₁-R₅)-phenyl-3-methyl-penta-2,4-dien-1-ol or a corresonding halide with apreviously described sulphinic acid or with an alkali metal saltthereof.

Compounds of formula II in which m is zero and A is formyl [IIg] can beprepared, for example, by formylating a (R₁ -R₅)-benzene in the mannerpreviously described. In this manner, there is obtained directly the (R₁-R₅)-benzaldehyde.

Compounds of formula II in which m is 1 and A is formyl (IIh) can beprepared, for example, by reacting a (R₁ - R₅)-phenyl-but-3-en-2-one(described hereinbefore in connection with the preparation of compoundsof formula IIb) under the conditions of a Wittig reaction withethoxycarbonyl-methylene-triphenyl-phosphorane or withdiethyl-phosphonacetic acid ethyl ester. The resulting (R₁-R₅)-phenyl-3-methyl-penta-2,4-dien-1-oic acid ethyl ester issubsequently reduced in the cold by means of a mixed metal hydride,especially lithium aluminium hydride, in an organic solvent (e.g. etheror tetrahydrofuran) to give a (R₁ -R₅)-phenyl-3-methylpenta-2,4-dien-1-ol. This alcohol is then oxidised bytreatment with an oxidising agent (e.g. manganese dioxide in an organicsolvent such as acetone or methylene chloride) at a temperature between0° C. and the boiling point of the oxidation mixture to give the desired(R₁ -R₅)-phenyl-3-methyl-penta-2,4-dien-1-al of formula IIh.

The compounds of the formula III are, in part, novel.

Compounds of formula III in which the symbol n is zero and B istriarylphosphoniummethyl [IIIa] or a dialkoxyphoshinylmethyl group[IIIc] can be readily prepared by reacting a 4-halo-3-methyl-crotonicacid, which may be esterified, or an etherified 4-halo-3-methyl-crotylalcohol with a triarylphosphine in a solvent, preferably withtriphenylphosphine in toluene or benzene, or with a trialkylphosphite,especially with triethylphosphite.

Compounds of formula III in which n is 1 and B istriarylphosphoniummethyl [IIIb] or dialkoxyphosphinylmethyl [IIId] canbe prepared, for example, by reducing the formyl group in an aldehyde offormula III, in which n is 1 and B is formyl [IIIh] to the hydroxymethylgroup using a metal hydride such as sodium borohydride in an alkanol(e.g. ethanol or isopropanol). The resulting alcohol can be halogenatedusing a customary halogenating agent (e.g. phosphorus oxychloride) andthe resulting 8-halo-3,7-dimethyl-octa-2,4,6-triene-1-carboxylic acid, ahalide of formula III in which n is 1 and B is halomethyl [IIIk], or aderivative thereof can be converted with a triarylphosphine in asolvent, preferaby triphenylphosphine, in toluene or benzene, or with atrialkylphosphite, especially triethylphosphite, into a desiredphosphonium salt of formula IIIb or phosphonate of formula IIId.

Compounds of formula III in which n is zero and B is sulphonylmethyl[IIIe] can be prepared, for example, by reacting4-hydroxy-3-methyl-but-2-en-1-al or the acetate thereof or thecorresponding bromide in a polar solvent (e.g. isopropanol or n-butanol)in the manner previously described with an aforementioned sulphinic acidor with an alkali metal salt thereof.

Compounds of formula III in which n is 1 and B is sulphonylmethyl [IIIf]can be prepared in a manner analogous to that previously described bythe reaction of, for example, 8-hydroxy-3,7-dimethyl-octa-2,4,6-trien-1-oic acid or the acetate thereof or a corresponding bromidewith an aforementioned sulphinic acid.

Compounds of formula III in which n is zero and B is formyl [IIIg] canbe prepared, for example, by oxidatively cleaving an optionallyesterified tartaric acid (e.g. using lead tetraacetate at roomtemperature in an organic solvent such as benzene). The glyoxalic acidderivative obtained is subsequently condensed in a manner known per se,conveniently in the presence of an amine, with propionaldehyde at anelevated temperature (e.g. a temperature between 60° C. and 110° C.)with loss of water to give a desired 3-formyl-crotyl alcohol derivative.

Compounds of formula III in which n is 1 and B is formyl [IIIh] can beprepared, for example, by allowing phosgene to act on4,4-dimethoxy-3-methyl-but-1-en-3-ol in the cold, preferably at -10° C.to -20° C. in the presence of a tertiary amine such as pyridine andcondensing the resulting 2-formyl-4-chloro-but-2-ene under theconditions of a Wittig reaction with 3-formyl-crotonic acid, which maybe esterified, or with a 3-formyl-crotyl alcohol, which may beesterified, to give the desired aldehyde of formula IIIh.

In accordance with the process provided by the present invention, aphosphonium salt of formula IIa or IIb is reacted with an aldehyde offormula IIIh or IIIg, or a phosphonium salt of formula IIIa or IIIb isreacted with an aldehyde of formula IIh or IIg, or a phosphonate offormula IIc or IId is reacted with an aldehyde of formula IIIh or IIIg,or a phosphonate of formula IIIc or IIId is reacted with an aldehyde offormula IIh or IIg, or a sulphone of formula IIe or IIf is reacted witha halide of formula IIIk or IIIi or a sulphone of formula IIIe or IIIfis reacted with a halide of formula IIk or IIi.

According to the Wittig procedure, the components are reacted with oneanother in the presence of an acid-binding agent (e.g., an alkali metalalcoholate such as sodium methylate or an alkylene oxide which may bealkyl-substitited, especially ethylene oxide or 1,2-butylene oxide), orif desired in a solvent (e.g. a chlorinated hydrocarbon such asmethylene chloride, or dimethylformamide), at a temperature between roomtemperature and the boiling point of the reaction mixture.

According to the Horner procedure, the components are reacted togetherusing a base and preferably in the presence of an inert organic solvent,for example, sodium hydride in benzene, toluene, dimethylformamide,tetrahydrofuran or 1,2-dimethoxyethane, or also sodium methylate inmethanol, at a temperature between 0° C. and the boiling point of thereaction mixture.

According to the Julia procedure, the components are reacted with oneanother using a condensation agent, conveniently in the presence of apolar solvent. Suitable solvents are, for example, dimethylformamide,dimethyl sulphoxide, dimethylacetamide, tetrahydrofuran andhexamethylphosphoric acid triamide as well as alcohols such as methanol,isopropanol or terbutanol. Of the strong bases which are particularlyuseful as the condensation agents there can be mentioned, for example,alkali metal and alkaline earth metal carbonates, especially sodiumcarbonate, alkali metal hydroxides such as potassium hydroxide or sodiumhydroxide, alkali metal and alkaline earth metal alcoholates such assodium methylate and, especially, potassium terbutylate, alkali metalhydrides such as sodium hydride, alkylmagnesium halides such asmethyl-magnesium bromide and alkali metal amides such as sodium amide.The reaction using this procedure is preferably carried out at a lowtemperature, especially at a temperature below the freezing point (e.g.between -50° C. and -80° C.)

It has been found to be convenient in certain cases to carry out theaforementioned reactions in situ; that is to say, without isolating theparticular phosphonium salt, phosphonate or sulphone from the medium towhich it is prepared.

A carboxylic acid of formula I can be converted in a manner known per se(e.g. by treatment with thionyl chloride, preferably in pyridine) intoan acid chloride which can be converted into an ester by reaction withan alkanol and into an amide by reaction with ammonia.

A carboxylic acid ester of formula I can be hydrolysed to a carboxylicacid in a manner known per se; for example, by treatment with an alkali,especially aqueous-alcoholic sodium hydroxide or potassium hydroxide ata temperature between room temperature and the boiling point of themixture. The resulting carboxylic acid can then be amidated via an acidhalide. Alternatively, a carboxylic acid ester can be directly amidatedas described hereinafter.

A carboxylic acid ester of formula I can be converted directly into acorresponding amide by treatment with lithium amide. This treatment isadvantageously carried out at room temperature.

A carboxylic acid or a carboxylic acid ester of formula I can be reducedto a corresponding alcohol of formula I in a manner known per se. Thereduction is advantageously carried out using a metal hydride or alkylmetal hydride in an inert solvent. Examples of hydrides which haveproved to be particularly suitable are metal hydrides such as lithiumaluminium hydride and bis-[methoxy-ethylenoxy]-sodium aluminium hydride.Suitable inert solvents are, inter alia, ether, tetrahydrofuran ordioxane when lithium aluminium hydride is used and ether, hexane,benzene or toluene when diisobutylaluminium hydride orbis-[methoxy-ethylenoxy]-sodium aluminium hydride is used.

An alcohol of formula I can be etherified with an alkyl halide (e.g.ethyl iodide), for example in the presence of a base, preferably sodiumhydride, in an organic solvent such as dioxane, tetrahydrofuran,1,2-dimethoxyethane or dimethylformamide, or in the presence of analkali metal alcoholate in an alkanol, at a temperature between 0° C.and room temperature.

An alcohol of formula I can also be esterified by treatment with analkanoyl halide or anhydride, expediently in the presence of a base(e.g. pyridine or triethylamine) at a temperature between roomtemperature and the boiling point of the mixture.

An alcohol ester obtained can be saponified in a manner known per se;for example in the manner previously described in connection with thesaponification of a carboxylic acid ester.

An alcohol of formula I or an ester thereof can be oxidised in a mannerknown per se to give a corresponding acid of formula I. The oxidation isadvantageously carried out using silver (I) oxide an alkali in water orin a water-miscible organic solvent at a temperature between roomtemperature and the boiling point of the mixture.

An amine of formula I forms acid addition salts with inorganic acids(e.g. hydrohalic acids, especially hydrochloric acid or hydrobromicacid, and sulphuric acid) and with organic acids (e.g. benzoic acid,acetic acid, citric acid and lactic acid). A carboxylic acid of formulaI forms salts with bases, especially with alkali metal hydroxides andparticularly with sodium hydroxide and potassium hydroxide.

The compounds of formula I can occur as a cis/trans mixture which may beseparated in a manner known per se into the cis and trans components orisomerised in a manner known per se to the all-trans compounds.

The present polyene compounds of formula I are pharmacodynamicallyvaluable. They are effective in regressing the growth of tumors such aspapillomas.

The compounds of formula I are also useful as medicaments for thetopical and systemic therapy of acne, psoriasis and other relateddermatological disorders which are characterized by an increased orpathologically altered cornification, as well as inflammatory andallergic dermatological conditions. They can also be used to treatdisorders which are characterized by inflammatory or degenerativealterations of the mucous membranes.

The toxicity of the present polyene compounds is slight. For examplewhen9-(2-chloro-4-methoxy-3,5,6-trimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid is administered intraperitoneally to mice weighing 30 g. in a dailydosage of 200 mg/kg, then no indication of an A-hypervitaminosis becomesevident after 14 days [total of 10 administration days].

The first indications of a light A-hypervitaminosis in mice appears at adaily dosage of 400 mg/kg after 14 days [total of 10 administrationdays]. This manifests itself in a weight decrease of 20%, a moderatehair loss and slight flaking of the skin.

The tumour-inhibiting activity of the present polyene compounds issignificant. In the papilloma test, tumours induced withdimethylbenzanthracene and croton oil regress. The diameter of thepapillomas within 2 weeks after the intraperitoneal administration of9-(2-chloro-4-methoxy-3,5,6-trimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester decreases by 61% at a dosage of 400 mg/kg/week and by45% at a dosage of 200 mg/kg/week.

The polyene compounds of formula I and their salts can therefore be usedas medicaments; for example, in the form of pharmaceutical preparationswhich contain them in association with a compatible pharmaceuticalcarrier.

The pharmaceutical preparations for systemic administration can beprepared, for example, by adding a polyene compound as the activeingredient to non-toxic inert solid or liquid carriers which are usualin such preparations.

The pharmaceutical preparations can be administered enterally orparenterally. Suitable preparations for enteral administration are, forexample, tablets, capsules, dragees, syrups, suspensions, solutions andsuppositories and suitable preparations for parenteral administrationare infusion and injection solutions.

The dosages in which the polyene compounds of this invention areadministered can be varied according to the mode and route ofadministration and according to the requirements of the patient.

The polyene compounds of this invention can be administered in amountsof from 5 mg. to 200 mg. daily in one or more dosages. Capsulescontaining ca 10 mg. to ca 100 mg. of a polyene compound of thisinvention represent a preferred form of administration.

The pharmaceutical preparations can contain inert or pharmacodynamicallyactive ingredients. Tablets or granules, for example, can contain aseries of binders, fillers, carrier materials or diluents. Liquidpreparations can, for example, take the form of a sterile water-misciblesolution. Capsules can contain a filler or thickener. Furthermore,flavour-improving additives and substances commonly used aspreservatives, stabilisers, moisture-retainers or emulsifiers, salts forvarying the osmotic pressure, buffers and other additives can also bepresent in the pharmaceutical preparations.

The aforementioned carrier materials and diluents can be organic orinorganic substances such as water, gelatin, lactose, starch, magnesiumstearate, talc, gum arabic, polyalkyleneglycols and the like. It is, ofcourse, a prerequisite that all adjuvants used in the preparation of thepharmaceutical preparations are non-toxic.

For topical administration, the present polyene compounds areexpediently made up in the form of ointments, tinctures, creams,solutions, lotions, sprays, suspensions and the like. Ointments, creamsand solutions are preferred. These pharmaceutial preparations fortopical administration can be prepared by mixing the polyene compounds,as the active ingredient, with non-toxic inert solid or liquid carrierswhich are customary in such preparations and which are suitable fortopical treatment.

Expedient for topical administration are ca 0.01% to ca 0.3% preferably0.02% to 0.1%, solutions and ca 0.05% to ca 5%, preferably ca 0.1% to ca2.0%, ointments or creams.

An antioxidant (e.g. tocopherol, N-methyl-γ-tocopheramine, butylatedhydroxyanisole or butylated hydroxytoluene) can also be present in thepharmaceutical preparations.

The compounds of formula I are utilized as salts with pharmaceuticallyacceptable acids and bases. These salts can be prepared utilizingconventional methods of preparing these salts.

The following Examples illustrate the present invention. In theExamples, the term "normal conditions" designates normal pressure androom temperature. The term "low boiling point petroleum ether"designates a fraction of petroleum ether boiling at 30° to 45° C. Theterm "5% palladium on carbon" designates a catalyst containing 5% byweight palladium on 95% by weight carbon. In the Examples, the etherutilized is diethyl ether and the temperature is in degrees Centigrade(° C.).

EXAMPLE 1

9.9 g. of 2-chloro-4-methoxy-3,5,6-trimethyl-benzyl-triphenylphosphoniumchloride are dissolved in 50 ml. of dimethylformamide. After theaddition of 4.16 g. of 7-formyl-3-methyl-octa-2,4,6-trien-1-oic acidethyl ester, the solution is treated dropwise at 20° C. with 10 ml. of asolution of sodium ethylate freshly prepared from 0.460 g. of sodium and10 ml. of absolute ethanol. The mixture is stirred at room temperaturefor 12 hours, then introduced into 100 ml. of water and extracted withhexane. The hexane extract is shaken out three times withmethanol/water, dried over sodium sulphate and evaporated under reducedpressure. The residue is purified by absorption on silica gel usingmethylene chloride/hexane (8:2 parts by volume) for the elution. The9-(2-chloro-4-methoxy-3,5,6-trimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester obtained from the eluate melts at 90° C. afterrecrystallisation from hexane.

EXAMPLE 2

189 g. of 3-chloro-4,6-dimethyl-benzyl chloride are introduced into 1500ml. of 5-N aqueous sodium hydroxide. The mixture is treated whilestirring with 195 g. of zinc dust within 2 hours. The temperature of thereaction, which takes place exothermically, is maintained at 70° C. bycooling. The mixture is stirred for a further 12 hours at 50° C. andsubsequently filtered. The filtrate is extracted three times with 800ml. of ethylene chloride. The methylene chloride extract is washedneutral with water, dried over sodium sulphate and evaporated. Theresidual 2-chloro-b 3,5,6-trimethyl-benzene is purified by adsorption onsilica gel using hexane/methylene chloride (9:1 parts by volume) for theelution. The compound boils at 81° C./9 mm Hg.

70 g. of 2-chloro-3,5,6-trimethyl-benzene are added dropwise within 30minutes while stirring to 400 ml. of aqueous nitric acid [70% v/v]pre-cooled to 0° C. The mixture is stirred for a further 4 hours at aslowly increasing temperature up to 20° C., then introduced intoice-water and thoroughly extracted with diethyl ether. The ether extractis washed six times with 1000 ml. of water, dried over sodium sulphateand evaporated under reduced pressure. The residual2-chloro-4-nitro-3,5,6-trimethylbenzene is purified by adsorption onsilica gel using hexane/benzene (3:7 parts by volume) for the elution.The compound melts at 79° C. after recrystallization from low-boilingpetroleum ether.

114.5 g. of 2-chloro-4-nitro-3,5,6-trimethyl-benzene are dissolved in300 ml. of ethyl acetate. The solution is diluted with 300 ml. ofethanol and, after the addition of 20 ml. of Raney-nickel, hydrogenatedunder normal conditions. After the uptake of 43 liters of hydrogen, thehydrogenation is terminated. The catalyst is filtered off while gassingwith carbon dioxide and washed with ethanol. The combined filtrates areevaporated under reduced pressure. The residual4-amino-2-chloro-3,5,6-trimethyl-benzene melts at 93° C. afterrecrystallization from hexane.

65 g. of 4-amino-2-chloro-3,5,6-trimethyl-benzene are graduallyintroduced into 250 ml. of concentrated aqueous sulphuric acid whilestirring and cooling. In so doing, the temperature rises to +60° C. Themixture is cooled to 0° C. by the gradual addition of 750 g. of ice andthen treated dropwise within 3 hours with a solution of 26.4 g. ofsodium nitrite in 80 ml. of water. The mixture is stirred for a further90 minutes at 0° C. to +10° C. and subsequently filtered. The filtrateis subjected to a steam distillation while adding dropwise 600 ml. ofaqueous sulphuric acid [50 vol%]. The distillate is extracted threetimes with 1000 ml. of methylene chloride. The methylene chlorideextract is dried over sodium sulphate and evaporated. The residual2-chloro-4-hydroxy-3,5,6-trimethyl-benzene melts at 97° C. afterrecrystallization from hexane.

After the addition of 400 ml. of methanol and 85.5 ml. of dimethylsulphate, 76 g. of 2-chloro-4-hydroxy-3,5,6-trimethyl-benzene aretreated dropwise while stirring with 256.5 ml. of aqueous potassiumhydroxide [25% g/v]. The mixture, which thereby heats to boiling, isstirred for a further 4 hours under reflux conditions and subsequentlyevaporated. The residue is taken up in 600 ml. of water. The aqueoussolution is extracted three times with 600 ml. of diethyl ether. Theether extract is washed neutral with water, dried over sodium sulphateand evaporated under reduced pressure. The residual oily2-chloro-4-methoxy-3,5,6-trimethyl-benzene boils at 77°-79° C/1 mm Hg.

65.35 g. of 2-chloro-4-methoxy-2,5,6-trimethyl-benzene are mixed with235 ml. of acetic acid, 446 ml. of aqueous hydrochloric acid [37 g/v]and 107 ml. of aqueous formaldehyde (35% by weight). The mixture isstirred at 70° C. for 3 hours and, after coolings, introduced into 2000ml. of water. The aqueous solution is extracted three times with 1000ml. of methylene chloride. The methylene chloride extract is washedthree times with 1000 ml. of water, dried over sodium sulphate andevaporated. The residual 2-chloro-4-methoxy-3,5,6-trimethyl-benzylchloride is purified by adsorption on silica gel using low boilingpetroleum ether for the elution. The compound melts at 59°-63° C. afterrecrystallization from low boiling petroleum ether.

70.8 g. of 2-chloro-4-methoxy-3,5,6-trimethyl-benzyl chloride aredissolved in 500 ml. of toluene. The solution is treated with 77 g. oftriphenylphosphine and stirred at 100° C. for 18 hours. The2-chloro-4-methoxy-3,5,6-trimethyl-benzyl-triphenylphosphonium chloridewhich separates in the form of white crystals is washed with diethylether and dried in vacuo. The phosphonium salt melts at 215° C.

EXAMPLE 3

After the addition of a small amount of iron (III) nitrate, 2700 ml. ofliquid ammonia are treated portionwise with 169.5 g. of potassium whilestirring and cooling. As soon as the initially blue colour hasdisappeared (.i.e., after about 30-45 minutes), acetylene gas isintroduced in a stream of three liters per minute until the dark colourof the mixture becomes lighter. Then the gas stream is reduced to twoliters per minute and the mixture treated dropwise with a solution of500 g. of methylglyoxal dimethylacetal in 425 ml. of absolute ether. Thegassing with acetylene is continued for a further 1 hour while stirring.The mixture is subsequently treated portionwise with 425 g. of ammoniumchloride, gradually warmed to 30° C. within 12 hours while evaporatingthe ammonia and extracted with 1600 ml. of diethyl ether. The etherextract is dried over sodium sulphate and evaporated under reducedpressure. The residual 4,4-dimethoxy-3-methylbut-1-yne-3-ol boils, afterrectification, at 33° C/0.03 mmHg; n.sub. D²⁵ = 1.4480.

198 g. of 4,4-dimethoxy-3-methyl-but-1-yne-3-ol are dissolved in 960 ml.of high boiling petroleum ether and, after the addition of 19.3 g. of 5%palladium catalyst and 19.3 g. of quinoline, hydrogenated under normalconditions. After the uptake of 33.5 liters of hydrogen, thehydrogenation is terminated. The catalyst is filtered off. The filtrateis evaporated under reduced pressure. The residual4,4-dimethoxy-3-methyl-but-1-en-3-ol boils, after rectification, at70° - 72° C/18 mm Hg.

195 ml. of phosgene are introduced into 1570 ml. of carbon tetrachlorideat -10° C. After the addition of 213 g. of pyridine, the solution istreated dropwise with 327 g. of 4,4-dimethoxy-3-methyl-but-1-en-3-ol ata temperature of -10° C. to -20° C. The mixture is slowly warmed to 25°C. while stirring, stirred for a further 3 hours at room temperature,cooled to 15° C. and treated with 895 ml. of water. The aqueous phase isseparated and discarded. After standing for 12 hours in the cold, theorganic phase is treated with 448 ml. of 5% by weight aqueous sulphuricacid, stirred for 5 hours, then washed with water, dried over sodiumsulphate and evaporated under reduced pressure. The residual2-formyl-4-chloro-but-2-ene boils, after rectification, at 37° -40°C/1.8 mm Hg; n_(D) ²⁵ = 1.4895.

165.7 g. of 2-formyl-4-chloro-but-2-ene are dissolved in 840 ml. ofbenzene and treated with 367 g. of triphenylphosphine. The mixture isheated to boiling under reflux conditions for 12 hours while gassingwith nitrogen and then cooled to 20° C. The precipitated2-formyl-but-2-ene-4-triphenylphosphonium chloride melts at 250°-252° C.after washing with benzene and drying.

212.6 g. of 2-formyl-but-2-ene-4-triphenylphosphonium chloride and 95 g.of 3-formyl-crotonic acid ethyl ester are introduced into 1100 ml. ofbutanol and treated at 5° C. with a solution of 57 g. of triethylaminein 60 ml. of butanol. The mixture is subsequently stirred for 6 hours at25° C., then cooled, introduced into water and thoroughly extracted withhexane. The hexane phase is first washed repeatedly with methanol/water(6:4 parts by volume), then washed with water, dried over sodiumsulphate and filtered. The filtrate is isomerized by shaking with iodinefor 12 hours. The iodine is removed by the addition of sodiumthiosulphate. The filtrate is washed with water again, dried andevaporated under reduced pressure. The residual7-formyl-3-methyl-octa-2,4,6-trien-1-oic acid ethyl ester can be used inthe process without further purification.

EXAMPLE 4

39 g. of 2,6-dichloro-4-methoxy-benzyl-triphenylphosphonium chloride and16 g. of 7-formyl-3-methyl-octa-2,4,6-trien-1-oic acid ethyl ester areheated at 82°-85° C. under reflux conditions while stirring for 2 hoursafter the addition of 40 g. of 1,2-butylene oxide. The mixture is thenthoroughly extracted with hexane. The hexane extract is washed severaltimes with methanol/water (60:40 parts by volume), dried over sodiumsulphate and evaporated under reduced pressure. The residue is purifiedby absorption on silica gel using hexane for the elution. The9-(2,6-dichloro-4-methoxyphenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester obtained from the eluate melts at 117°-118° C. afterrecrystallization from hexane.

EXAMPLE 5

77 g. of 3,5-dichloro-anisole are dissolved in 250 ml. of ether. Afterthe addition of 70 ml. of aqueous formaldehyde [35% g/v], the solutionis gassed with hydrogen chloride at room temperature while stirring for8 hours. The solution is subsequently poured on to ice and thoroughlyextracted with diethyl ether. The ether extract is washed neutral withwater, dried over sodium sulphate and evaporated under reduced pressure.The residual oily 2,6-dichloro-4-methoxy-benzyl chloride has arefractive index of n_(D) ²⁴ = 1.5730.

23.7 g. of 2,6-dichloro-4-methoxy-benzyl chloride, 26.2 g. oftriphenylphosphine and 150 ml. of absolute benzene are heated for 12hours under reflux conditions. The2,6-dichloro-4-methoxy-benzyl-triphenylphosphonium chloride whichprecipitates on cooling is dried in vacuo before being used in theprocess.

EXAMPLE 6

By the procedure of Example1,2-chloro-4-methoxy-5,6-dimethyl-benzyltriphenylphosphonium chloride isreacted with 7-formyl-3-methyl-octa-2,4,6,-trien-1-oic acid ethyl esterto obtain9-(2-chloro-4-methoxy-5,6-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester, a yellow-red oil.

The 2-chloro-4-methoxy-5,6-dimethyl-benzyl-triphenylphosphonium chlorideused as the starting material is prepared in a manner analogous to thatdescribed in Examples 2 and 6, starting, for example, from2,3-dimethyl-aniline and proceeding via 2,3-dimethyl-5-nitro-aniline,2,3-dimethyl-5-nitro-phenol, 2,3-dimethyl-5-nitro-anisole,2,3-dimethyl-5-amino-anisole, 2,3-dimethyl-5-chloro-anisole and2-chloro-4-methoxy-5,6-dimethyl-benzyl chloride.

EXAMPLE 7

By the procedure of Example 1,2,3,6-trichloro-4-methoxy-benzyltriphenyl-phosphonium chloride isreacted with 7-formyl-3 -methyl-octa-2,4,6-trien-1-oic acid ethyl esterto obtain9-(2,3,6-trichloro-4-methoxyphenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester of melting point 126° - 128° C.

The 2,3,6-trichloro-4-methoxy-benzyl-triphenylphosphonium chloride usedas the starting material can be prepared in a manner analogous to thatdescribed in Examples 2 and 5 starting, for example, from2,3,5-trichloro-phenol and proceeding via 2,3,5-trichloro-anisole and2,3,6-trichloro-4-methoxy-benzyl chloride.

EXAMPLE 8

By the procedure of Example 1,2,4-dimethoxy-3,6-dimethyl-benzyltriphenyl-phosphonium chloride isreacted with 7-formyl-3-methyl-octa-2,4,6-trien-1-oic acid ethyl esterto obtain9-(2,4-dimethoxy-3,6-dimethylphenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.

The9-(2,4-dimethoxy-3,6-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid obtained by saponifying the foregoing ester melts at 214°-215° C.

The 2,4-dimethoxy-3,6-dimethyl-benzyl-triphenylphosphonium chloride usedas the starting material can be prepared in a manner analogous to thatdescribed in Example 2 starting, for example, from orcin(3,5-dihydroxy-toluene) and proceeding via2-acetyl-3,5-dihydroxy-toluene, 2-acetyl-3,5-dihydroxy-p-xylol,2,6-dihydroxy-p-xylol, 2,6-dimethoxy-p-xylol and2,4-dimethoxy-3,6-dimethyl-benzyl chloride.

EXAMPLE 9

By the procedure of Example 1,6-chloro-4-methoxy-2,5-dimethylbenzyl-triphenylphosphonium chloride isreacted with 7-formyl-3-methyl-octa-2,4,6-trien-1-oic acid ethyl esterto obtain9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester of melting point 106°-107° C.

The 6-chloro-4-methoxy-2,5-dimethyl-benzyl-triphenylphosphonium chlorideused as the starting material can be prepared in a manner analogous tothat described in Examples 2 and 5, starting, for example, from3-chloro-2,5-dimethyl-nitrobenzene and proceeding via3-chloro-2,5-dimethylaniline, 3-chloro-2,5-dimethyl-phenyl,3-chloro-2,5-dimethyl-anisole and 6-chloro-4-methoxy-2,5-dimethyl-benzylchloride.

EXAMPLE 10

41 g. of9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester are dissolved in 750 ml. of ethanol. The solution istreated with 41 g. of potassium hydroxide in 63 ml. of water, heated toboiling for 30 minutes under a nitrogen atmosphere, cooled, introducedinto water and acidified with hydrochloric acid. The precipitated9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethylnona-2,4,6,8-tetraen-1-oic acid melts at 231°- 234° C.

EXAMPLE 11

15 g. of9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid are dissolved in 750 ml. of tetrahydrofuran. The solution obtainedis treated with 2.64 ml. (0.7 mol) of phosphorus trichloride,concentrated after 12 hours to half of its volume at 30° C. underreduced pressure and added dropwise at 0°-5° C. to a tetrahydrofuransolution containing 14.6 g. of ethylamine. The mixture is stirred for 1hour at room temperature, introduced into a saturated aqueous sodiumchloride solution and extracted with methylene chloride. The extract iswashed with an aqueous sodium chloride solution, dried and evaporatedunder reduced pressure. The residual9-(6-chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl amide is purified by adsorption on silica gel using methylenechloride/methanol (90:10 parts by volume) for the elution. Afterrecrystallization from ethyl acetate, this ethyl amide melts at 202° C.to 203° C.

EXAMPLE 12

A capsule is prepared containing the following ingredients:

    ______________________________________                                        9-(2-Chloro-4-methoxy-3,5,6-trimethyl                                         phenyl)-3,7-dimethyl-nona-2,4,6,8-                                             tetraen-1-oic acid ethyl ester                                                                         10      mg.                                         Wax mixture               41.5    mg.                                         Vegetable oil             98.0    mg.                                         Trisodium salt of ethylenediamine-                                             tetraacetic acid         0.5     mg.                                         Individual weight of a capsule                                                                          150     mg.                                         Active ingredient content of a capsule                                                                  10      mg.                                         ______________________________________                                    

EXAMPLE 13

A salve is prepared containing 2.0% of active ingredient with thefollowing ingredients:

    ______________________________________                                        9-(2-Chloro-4-methoxy-3,5,6-trimethyl-                                         phenyl)-3,7-dimethyl-nona-2,4,6,8-                                            tetraen-1-oic acid ethyl ester                                                                          2.0 g.                                             Cetyl alcohol              2.7 g.                                             Lanolin                    6.0 g.                                             Petroleum jelly            15.0 g.                                            Distilled water q.s. ad    100.0 g.                                           ______________________________________                                    

We claim:
 1. A compound of the formula: ##STR10## wherein R₁ and R₂ arehalogen, lower alkyl or lower alkoxy, with the proviso that one of R₁and R₂ is halogen; R₃ and R₅ are hydrogen, halogen or lower alkyl; withthe proviso that one of R₃ and R₅ is other than halogen; R₄ is loweralkoxy; and R₆ is alkoxycarbonyl; and salts thereof.
 2. The compound ofclaim 1 wherein said compound is9-(6-Chloro-4-methoxy-2,3-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.
 3. The compound of claim 1 wherein said compound is9-(2-Chloro-4-methoxy-3,5,6-trimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.
 4. The compound of claim 1 wherein said compound is9-(2,6-Dichloro-4-methoxy-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.
 5. The compound of claim 1 wherein said compound is9-(2,5,6-Trichloro-4-methoxy-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.
 6. The compound of claim 1 wherein said compound ofclaim 1 wherein said compound is9-(6-Chloro-4-methoxy-2,5-dimethyl-phenyl)-3,7-dimethyl-nona-2,4,6,8-tetraen-1-oicacid ethyl ester.